Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
  • C23C22/53—Treatment of zinc or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/38—Chromatising
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2222/00—Aspects relating to chemical surface treatment of metallic material by reaction of the surface with a reactive medium
  • C23C2222/10—Use of solutions containing trivalent chromium but free of hexavalent chromium

Definitions

• the present invention relates to a treatment solution and a method for producing substantially chromium (VI) -free black conversion layers on zinc-containing alloy layers.
• chromium (VI) compounds whose essential component is chromium (VI) compounds.
• the generated conversion layer therefore also contains chromium (VI) ions.
• Chromating layers generally have good corrosion protection and good decorative properties.
• a disadvantage of the use of chromium (VI) -containing solutions or chromium (VI) -containing coatings are the toxicological properties of chromium (VI).
• the use of chromium (VI) -containing conversion layers is therefore, e.g. severely restricted by the EC directive 2000/53 / EC (EC end-of-life vehicle directive).
• chromium (III) -containing, acidic treatment solutions commonly referred to as “passivations” or “passivation solutions”, unlike chromations.
• passivations or “passivation solutions”
• These treatment solutions exist as in DE 196 15 664 A1 proposed essentially from a chromium (III) salt in mineral acid solution, a dicarboxylic acid or hydroxycarboxylic acid and a cobalt salt.
• Such processes known as "thick-film passivation” are used at elevated temperature, about 40-60 ° C., in order to achieve a passivation layer thickness on zinc surfaces which is adequate for corrosion protection.
• the metal alloyed with the zinc is suitable for zinc alloy surfaces such as zinc-iron or zinc-nickel or zinc-cobalt.
• zinc alloy surfaces such as zinc-iron or zinc-nickel or zinc-cobalt.
• the less noble zinc is dissolved out of the layer and the alloying metal finely distributed on the surface enriched.
• the surface is dark or almost black tinted.
• an additional oxidizing agent is used for the black passivation of zinc-nickel surfaces in order to promote the etching effect of the acid. The result is a black surface that does not provide significant corrosion protection.
• WO 03/05429 describes a similar conversion layer which is also made with a chromium (III) -containing, acidic treatment solution which still contains phosphate ions.
• This surface also has good decorative properties, but does not achieve adequate corrosion protection properties without further post-treatment steps such as sealing.
• EP 1 484 432 A1 describes chromium (III) -containing black passivation solutions for zinc alloy surfaces containing chromium (III) ions and nitrate as well as carboxylic acids such as tartaric acid, maleic acid, oxalic acid, succinic acid, citric acid, malonic acid or adipic acid. To improve the corrosion protection, the surfaces treated with it must be subjected to a subsequent sealing. The treatment solutions are used at temperatures above normal room temperature.
• US 2004/0156999 also describes a method for black passivation of zinc alloy surfaces.
• the treatment solutions contain, in addition to chromium (III) ions and phosphorus-containing anions, nitrate and an organic carboxylic acid.
• organic carboxylic acids include citric, tartaric, maleic, glyceric, lactic, glycolic, malonic, succinic, oxalic and glutaric acids.
• black-passivated zinc or zinc alloy surfaces can not yet be produced in a fully satisfactory manner using known processes.
• a disadvantage of the described method is in particular that it is not possible to produce a black zinc alloy surface, which provides a good base corrosion protection.
• aftertreatment steps are generally necessary in order to improve the anti-corrosive properties of the layer.
• the surface should simultaneously be given very good anti-corrosive properties.
• the invention provides a composition which yields such a treatment solution by dilution with water.
• the invention provides a method for black passivation of zinc-containing surfaces, wherein the surface to be treated is immersed in such a treatment solution.
• the invention is based on the empirically discovered finding that good aesthetic properties (appearance, uniformity and coloration) in combination with good anticorrosive properties can be achieved by using at least one first carboxylic acid as defined above together with at least one second carboxylic acid as defined above mentioned concentration conditions.
• the treatment solution is an acidic, aqueous solution.
• Their pH is preferably in the range of 1.4 to 2.5, more preferably in the range of 1.5 to 2.0.
• the first carboxylic acid is preferably an alkyl, aryl, alkenyl or alkynylcarboxylic acid. Apart from the carboxyl group it contains no polar, eg protic, groups. In particular, it contains none of the following groups: -OH, -SO 3 H -NH 2 , -NHR, -NR 2 , -NR 3 + (where R is for a C 1 -C 6 alkyl group is). However, the first carboxylic acid may contain the following groups: halogen, alkyl, aryl, vinyl, alkoxy and nitro groups.
• acids which are suitable as the first carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanecarboxylic acid, cyclopentanecarboxylic acid, acetylsalicylic acid, benzoic acid, nitrobenzoic acid, 3,5-dinitrobenzoic acid, sorbic acid, trifluoroacetic acid, 2-ethylhexanoic acid, Acrylic acid, chloroacetic acid, 2-chlorobenzoic acid, 2-chloro-4-nitrobenzoic acid, cyclopropanecarboxylic acid, methacrylic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, phenoxyacetic acid, isovaleric acid, pivalic acid, 2-ethylbutyric acid, furan-2-carboxylic acid, bromoacetic acid, crotonic acid, 2- Chloropropionic acid, dichloroacetic acid, cycl
• the first carboxylic acid is preferably acetic acid.
• the second carboxylic acid carrying at least one further polar group is preferably a di- or tri-carboxylic acid. Also suitable are amino acids.
• acids suitable as the second carboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, phthalic acid, terephthalic acid, tartaric acid, citric acid, malic acid, ascorbic acid, ethylenedinitrilotetraacetic acid, tetrahydrofuran-2 carboxylic acid, ethylenediaminetetraacetic acid, diethylenediaminepentaacetic acid, nitrilotriacetic acid, lactic acid, adipic acid, 4-aminohippuric acid, 4-aminobenzoic acid, 5-aminoisophthalic acid, L-aspartic acid, L-glutamine, L-glutamic acid, alanine, beta-alanine, L-arginine, L-asparagine, L-alanine, N, N-bis (2-hydroxyethoxy
• the carboxylic acids can also be introduced into the treatment solution in the form of their salts.
• the treating solution preferably additionally contains cobalt (II) ions in a concentration in the range of 0.1 g / L to 3 g / L, more preferably in the range of 0.2 g / L to 2 g / L, most preferably in Range from 0.5 g / l to 1 g / l.
• cobalt (II) ions in a concentration in the range of 0.1 g / L to 3 g / L, more preferably in the range of 0.2 g / L to 2 g / L, most preferably in Range from 0.5 g / l to 1 g / l.
• the treatment solution according to the invention serves to passivate zinc alloys, such as e.g. Zinc-iron, zinc-nickel or zinc-cobalt alloys.
• zinc alloys such as e.g. Zinc-iron, zinc-nickel or zinc-cobalt alloys.
• Zinc-iron alloys preferably contain 0.4 to 1 wt .-% iron, zinc-nickel alloys preferably contain 8 to 20 wt .-% nickel and zinc-cobalt alloys preferably contain 0.5 to 5 wt .-% Cobalt.
• alloys can be electrochemically deposited on a substrate or applied by other methods such as hot dip galvanizing or make up the material of the article to be treated.
• the ratio ⁇ c (C1) / c (C2) ⁇ * ⁇ c (Cr 3+ ) / c (NO 3 - ) ⁇ is in the range of 0.1 to 0.2.
• the surface to be treated is immersed in a treatment solution as described above.
• the temperature of the treatment solution is preferably in the range of 20 ° C to 60 ° C, more preferably in the range of 20 ° C to 40 ° C, most preferably in the range of 20 ° C to 30 ° C.
• the treatment time in the treatment solution is preferably between 10 s and 180 s, more preferably between 30 s and 120 s, most preferably between 45 s and 90 s.
• the passivation treatment is assisted by cathodic switching of the substrate in the passivation solution.
• the cathodic current density on the substrate is preferably between 0.05 A / dm 2 and 10 A / dm 2 , more preferably between 0.1 A / dm 2 and 5 A / dm 2 , most preferably between 0.1 A / dm 2 and 3 A / dm 2 .
• chromium (VI) -free passivating solutions for zinc-containing surfaces typically consist of a source of chromium (IIII) ions, one or more complexing agents such as fluoride and / or polybasic carboxylic acids, hydroxycarboxylic acids or aminocarboxylic acids.
• Chromium (III) is present in the electron configuration 3d 3 of the valence electrons and is known almost exclusively in aqueous solutions as an octahedrally coordinated ion. In this configuration, the ion has high ligand field stabilization energy (LFSE).
• the Cr (II) ion with the electron configuration 3d 4 has a significantly lower kinetic inhibition and therefore significantly faster ligand exchange reactions.
• Water ligands on chromium (III) exchange several orders of magnitude more slowly than chromium (II). If the ion is in the high-spin configuration, the reactivity is also accelerated by the Jahn-Teller effect that occurs here.
• the high-spin arrangement of the electrons in the octahedral complex is observed with ligands that generate a comparatively weak ligand field, such as water, oxide.
• the low-spin case is only observed for ligands that are very strong Create ligand field.
• ligands are not included in the treatment solutions according to the invention.
• Carboxylate ions which are part of the treatment solutions according to the invention, belong to the former class, ie to ligands which generate a weak ligand field and thus form high-spin complexes.
• the reduction of Cr (III) to Cr (II) can also be carried out electrochemically. That is, by cathodic connection of the part to be passivated in the reaction solution, the layer formation reaction can be supported or carried out entirely by electrochemical means. Optionally, this process, especially on black passivated zinc surfaces, leads to an improvement of the corrosion protection.
• the construction of a dense, low-defect passivation layer is difficult.
• finely divided alloy metal e.g., cobalt, nickel, or iron
• the oxides of these elements are produced.
• blackening is accomplished by depositing small amounts of these more precious metals in comparison to the zinc by immersing the zinc surface in an e.g. Solution containing iron, nickel, cobalt, silver or copper ions by cementation.
• Charge exchange forms a thin layer of finely divided black metals or, depending on the treatment solution of the metal oxides, also non-stoichiometric zinc oxides.
• the Cr (II) possibly coordinated by these acids or their anions is not converted into a slightly soluble form and can be so the surface no or no sufficient enrichment for the purpose.
• acetic acid or acetate ions to convert Cr (II) into a sparingly soluble form is used for the preparative preparation of chromium (II) acetate (see the following formula).
• the binuclear structure as found for the chromium (II) acetate is not a prerequisite for the mode of action described in this invention. Intermediate polynuclear complexes with more than one chromium ion or even mononuclear complexes can also occur.
• Chromium (II) acetate forms red crystals that are oxidized to Cr (III) species in contact with atmospheric oxygen.
• the surface-enriched chromium species may undergo partial or complete ligand exchange to form a three-dimensional network.
• the pH of the solution was adjusted to pH 1.5 each with nitric acid or sodium hydroxide.
• a steel component was coated in a zinc-nickel alkaline alloy electrolyte (trade name: Reflectalloy ZNA, manufactured by Atotech) with a 5 ⁇ m-thick layer of a nickel-nickel-containing zinc-nickel alloy.
• the steel member was then immersed in a nitric acid-water mixture (about 0.3% HNO 3) at 20 ° C for 10 seconds to activate the surface, which was then rinsed with demineralized water and immediately poured into the reaction solution 1 above 2 and immersed at 25 ° C. for 60 s, then rinsed with demineralized water and dried, the surface of the part assuming a matte, dark to dark brown color in the salt spray test according to DIN 50021 SS ⁇ 12 h white corrosion.
• Aqueous reaction solutions having the compositions shown in Table 1 were prepared (the individual components were added in the same form as in Comparative Example 2). The pH of the solution was adjusted to the value shown in Table 1 with nitric acid or sodium hydroxide, respectively.
• Embodiment 3 was repeated except that the concentrations of acetic acid and oxalic acid were changed as shown in Table 2, respectively.
• the results of the evaluation of the coloring and the corrosion properties are also shown in Table 2.
• Table 1 Table 1
• Comparative example 3 4 Cr 3+ 4.5 g / l 4.5 g / l NO 3 - 17 g / l 17 g / l CO 2+ 0.3 g / l 0.3 g / l formic acid 0g / l 0g / l acetic acid 5 g / l 1 g / l propionic 0g / l 0g / l benzoic acid 0g / l 0g / l Oxalic acid dihydrate 1 g / l 9 g / l maleic 1.5 g / l 1.5 g / l pH 1.5 1.5 temperature 25 ° C 25 ° C exposure time 60 s 60 s Substrate (
• Comparative Example 3 shows that if the concentration of carboxyl groups from monocarboxylic acids is too high, only poor coloration of the treated surface is achieved.
• Comparative Example 4 shows that when the concentration of carboxyl groups of polycarboxylic acids is too high, only poor corrosion properties of the treated surface are obtained.

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• 2007
  • 2007-03-05 EP EP07103538A patent/EP1970470B1/fr not_active Not-in-force
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